The long-term objectives of this program are to understand and control human obesity and its deleterious consequences. To this end research with a major focus on genetic contributions to human obesity is proposed. The specific aims are: 1. FURTHER STUDIES OF DANISH ADOPTEES: (a) to analyze data already collected on siblings and half-siblings; (b) to conduct a preliminary analysis of major gene involvement by means of commingling analysis; (c) to analyze data on the childhood weight patterns of the adoptees; (d) to conduct path analyses of the entire data set (childhood and adult weights of adoptees and of their biologic and adoptive parents, siblings and half- siblings). 2. OTHER A. A genetic family study of three patient populations to identify patient characteristics that are related to increased risk of obesity in their first degree relatives. B. A genetic family study of obesity among the Old Order Amish of Lancaster County. C. An English follow-up study of children identified as being at increased or decreased risk of obesity when they were four years of age on the basis of parental obesity (or its absence) in the parents and a reduced (or average) energy expenditure. The study is designed to determine the body composition and energy expenditure of these children who are now 16 years of age. D. Commingling analysis of twin data to search for major gene involvement.